© 2017 Elsevier B.V. A DC thermal sensor based on a single metal-oxide-semiconductor field-effect transistor (MOSFET) is proposed to extract high-frequency electrical features of embedded circuits. The MOSFET sensor is monolithically integrated with the circuit under test (CUT) and then monitors by thermal means the DC power dissipated by the CUT, which carries high-frequency electrical information. After explaining the theory behind this testing approach, the paper demonstrates the feasibility of the proposed MOSFET sensor through simulations and experiments. These are carried out using a radio-frequency (RF) power amplifier as a CUT and thermally extracting its central frequency (440 MHz). The MOSFET sensor results are assessed using an infrared camera as a reference. The main advantage of the proposed sensing method is that the impact on the integrated circuit (IC) layout area is minimum, which is crucial when testing RF-ICs. Moreover, in comparison with previous works, the cost and complexity of the required instrumentation is lower.